True, but, they are, as you say "add-ons" not everyone gets them, either because they were "contracted out", or, for some of the add-ons because their earnings were lower. Also, unless I am being robbed, the "add-ons" do not appear to increase annually with inflation, or, if they do, they do not increase at the same rate as the basic state pension, thus, causing erosion of their value.
As I said earlier, IMHO, we have all been shafted wrt to State Pension.
some of us may not even get a state pension in the future....so be lucky your getting one